package com.wc.acwing.思维.回文数组;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

/**
 * @Author congge
 * @Date 2025/4/3 21:35
 * @description
 * https://www.acwing.com/problem/content/5996/
 */
public class Main {
    /**
     * 思路：直接比较, 如果相邻的是同号就抵消, 异号就没有了
     */
    static FastReader sc = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);
    static int N = 100010;
    static int[] a = new int[N];
    static int n;

    public static void main(String[] args) {
        n = sc.nextInt();
        for (int i = 1; i <= n; i++) a[i] = sc.nextInt();
        boolean sign = a[1] < a[n];
        long res = 0, d = 0;
        for (int i = 1, j = n; i < j; i++, j--) {
            boolean tmp = a[i] < a[j];
            int x = Math.abs(a[j] - a[i]);
            if (sign == tmp) {
                res += Math.max(0, x - d);
                // 细节 抵消
                if (x > d) d = x - d;
                // 全部抵消
                else d = 0;
            }
            else {
                res += x;
                d = x;
            }
            sign = tmp;
        }
        out.println(res);
        out.flush();
    }
}
class FastReader {
    StringTokenizer st;
    BufferedReader br;

    FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    String nextLine() {
        String s = "";
        try {
            s = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return s;
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    // 是否由下一个
    boolean hasNext() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                String line = br.readLine();
                if (line == null)
                    return false;
                st = new StringTokenizer(line);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return true;
    }
}

